The present invention relates to integration of a semiconductor laser and a photo-detector for monitoring the output light thereof.
A distributed feedback laser (hereinafter referred to as a DFB laser) is an excellent laser which performs single longitudinal mode oscillation, and it is usable as a light source for high quality optical fiber communications. In case of monitoring the output light of the conventional semiconductor laser, a monitor is provided at the outside or in combination with the distributed feedback laser. However, it is very difficult to associate a monitor with a distributed feedback laser so as to effectively and stably detect the output light of the distributed feedback laser.